Liquid fuels, and in particular diesel fuels, are colour coded for governmental tax purposes. For example, the amount of tax charged by governmental bodies on diesel fuel destined for agricultural use is different than diesel fuel destined for use by transport trucks. The tax on fuel is collectible by the fuel supplier, usually the petroleum company, and in order for the governmental bodies to be able to monitor that the correct taxes have been paid by the user the fuel is colour coded.
The fuel dye is usually provided to petroleum companies by the governmental body responsible for levying taxes on fuel. Usually, a volume of a known concentration of dye is provided to the petroleum company to be mixed with undyed fuel in a particular ratio to produce the dyed fuel. Since the governmental body specifies the final concentration of dye in the fuel, they can collect taxes based upon the amount of concentrate provided to the petroleum company as a measure of the amount of dyed fuel sold. Governmental authorities routinely check on the concentration of dye in dyed fuels to ensure that it meets with their specifications and thus provides an accurate measure of dyed fuels sold. Precise calibration of the mixing of fuel and dye is therefore extremely important. The amount of undyed fuel sold is calculated for tax purposes by taking the measurement of total fuel sold and subtracting from it the amount of dyed fuel that the known volume of dye provided to the supplier would have made.
Presently, it is necessary to maintain separate storage tanks at bulk terminals for dyed and undyed fuel. It is also necessary for trucks delivering the fuel to the end user to either carry only one variety of fuel at a time or to have multiple tanks on the truck. This creates a number of logistical problems as well as requiring increased storage capacity and a relatively large fleet of delivery trucks to ensure sufficient delivery capacity. Furthermore, when a tank-truck has been used to deliver one particular fuel, and it is needed to deliver another, the tank, hose and pump must be completely flushed and this adds to both time and overhead in the delivery process. A need therefore exists for a delivery system which is capable of carrying unmarked (i.e. undyed) fuel and at the point of delivery to the user providing either dyed or undyed fuel. Furthermore, because of the taxes levied on the fuel is based upon the amount of dye provided to the fuel supplier, extremely precise measurement of the amount of dye added to the fuel is required. Additionally, for security purposes, the driver delivering the fuel should not be able to access the dye injection system. He should only be able to select either dyed or undyed fuel.
A variety of additive injection systems are presently known. For example, U.S. Pat. No. 3,225,962 discloses a method specifically directed to adding odorants to liquid propane gas at bulk facilities when using automatic dispensing to a tank truck. The additive flow is metered and automatic shut-off of the main flow is provided where additive flow is too low. The additive is maintained under pressure and driven by a compressed gas. This system is of unknown accuracy and does not solve the problem of requirement of multiple products at the point of delivery.
U.S. Pat. No. 3,964,294 discloses a system for adding active tags to petroleum products for identification of the source of the product should they be involved in a spill. The system does not teach or suggest a constant metered addition of an additive into a stream of fuel, instead a bulk crudely measured amount of tracer is added.
U.S. Pat. No. 4,005,803 discloses a sprayer apparatus in which chemical concentrates are added to water for spraying behind a moving piece of farm equipment. Water pressure range determines whether the injection is terminated. A constant water flow rate is provided with the amount of injection, which is not metered, but which varies with the ground speed of the implement.
U.S. Pat. No. 4,276,997 discloses a system which injects anti icing additives into aircraft fuel tanks. It utilizes a series of discreet additive injections each time a measured amount of fuel is delivered. The calibration of this system is controlled by the operator and the additive is added prior to the delivery hose.
U.S. Pat. No. 5,222,027 discloses a system for remote control and monitoring of additive injection at a fuel terminal. It is a stationary system in which the concentrations are set by the users.